From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263305AbTEIQbx (ORCPT ); Fri, 9 May 2003 12:31:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263307AbTEIQbx (ORCPT ); Fri, 9 May 2003 12:31:53 -0400 Received: from 136.231.118.64.mia-ftl.netrox.net ([64.118.231.136]:1201 "EHLO smtp.netrox.net") by vger.kernel.org with ESMTP id S263305AbTEIQbv (ORCPT ); Fri, 9 May 2003 12:31:51 -0400 Subject: Re: how to measure scheduler latency on powerpc? realfeel doesn't work due to /dev/rtc issues From: Robert Love To: William Lee Irwin III Cc: Chris Friesen , Linux Kernel Mailing List In-Reply-To: <20030509070142.GU8978@holomorphy.com> References: <3EBAD63C.4070808@nortelnetworks.com> <20030509001339.GQ8978@holomorphy.com> <20030509003825.GR8978@holomorphy.com> <3EBB25FD.7060809@nortelnetworks.com> <20030509042659.GS8978@holomorphy.com> <3EBB4735.30701@nortelnetworks.com> <20030509062008.GT8978@holomorphy.com> <3EBB504C.1030001@nortelnetworks.com> <20030509070142.GU8978@holomorphy.com> Content-Type: text/plain Message-Id: <1052498824.867.8.camel@icbm> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.3.3 (1.3.3-2) (Preview Release) Date: 09 May 2003 12:47:05 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2003-05-09 at 03:01, William Lee Irwin III wrote: > Why not just keep track of it in the scheduler? The statistic is well- > defined in terms of things measurable at context switch and wakeup. This would measure context switch latency. Or something. By definition, scheduling latency is the time from an interrupt which wakes the task up until the task is actually running. Historically, it has been measured by things like realfeel or amlat or whatever which generate interrupts and wake a waiting task up. You then measure the latency between the interrupt and when the task actually runs in user-space. So Chris can then go run this test under varying loads and see how bad the latency gets. I understand his question, but (sorry Chris) I have no idea of the solution on PPC. Robert Love